As with the electronics and computer industries, trends in chemical and biochemical analysis are moving toward faster, smaller and less expensive systems and methods for performing all types of chemical and biochemical analyses.
The call for smaller systems and faster methods has been answered, in part, through the development of microfluidic technologies, which perform chemical and biochemical analyses and syntheses in extremely small-scale integrated fluid networks. For example, published International Patent Application No. WO 98/00231 describes microfluidic devices, systems and methods for performing a large number of screening assays within a single microfluidic device that is on the order of several square centimeters. Such developments have been made possible by the development of material transport systems that are capable of transporting and accurately dispensing extremely small volumes of fluid or other materials. See Published International Application No. 96/04547 to Ramsey.
By accurately controlling material transport among a number of integrated channels and chambers, one is able to perform a large number of different analytical and/or synthetic operations within a single integrated device. Further, because these devices are of such small scale, the amount of time for reactants to transport and/or mix, is very small. This results in a substantial increase in the throughput level of these microfluidic systems over the more conventional bench-top systems.
By reducing the size of these microfluidic systems, one not only gains advantages of speed, but also of cost. In particular, these small integrated devices are typically fabricated using readily available microfabrication technologies available from the electronics industries which are capable of producing large numbers of microfluidic devices from less raw materials. Despite these cost savings, it would nonetheless be desirable to further reduce the costs required to manufacture such microfluidic systems.
A number of reporters have described the manufacture of microfluidic devices using polymeric substrates. See, e.g., Published International Patent Application No. WO 98/00231 and U.S. Pat. No. 5,500,071. In theory, microfabrication using polymer substrates is less expensive due to the less expensive raw materials, and the xe2x80x98mass productionxe2x80x99 technologies available to polymer fabrication and the like.
However, despite these cost advantages, a number of problems exist with respect to the fabrication of microfluidic devices from polymeric materials. For example, because polymeric materials are generally flexible, a trait that is accentuated under certain fabrication methods, e.g., thermal bonding, solvent bonding and the like, it is difficult to accurately manufacture microscale structural elements in such polymeric materials. In particular, the microscale structures are easily deformed under manufacturing conditions, either due to applied pressures or relaxation of the polymer matrix based upon its intrinsic structural properties.
Accordingly, it would generally be desirable to have a method of fabricating microscale devices where the structural aspects of the device are not substantially perturbed during the fabrication process. The present invention meets these and other needs.
It is a general object of the present invention to provide methods of fabricating polymeric microfluidic devices, and the devices fabricated using these methods. In a first aspect, the present invention provides for methods of fabricating a microfluidic device comprising a first substrate having a first planar surface, and a second substrate layer having a first planar surface, wherein the first planar surface of the first substrate comprises a plurality of microscale grooves disposed therein. The first planar surface of the second substrate is heated approximately to the transition temperature of the first surface of the second substrate without heating the first surface of the first substrate approximately to the transition temperature of the first surface of the first substrate. The first surface of the first substrate is then bonded to the first surface of the second substrate.
This invention also provides methods of fabricating a microfluidic device comprising a first substrate having a first planar surface, and a second substrate layer having a first planar surface wherein the first planar surface of the first substrate comprises a plurality of microscale grooves disposed therein, and the first planar surface of the second substrate has a lower transition temperature than the first surface of the first substrate. The first planar surface of the second substrate is heated approximately to its transition temperature. The first surface of the first substrate is then bonded to the first surface of the second substrate.
This invention also provides methods of fabricating microfluidic devices comprising a first substrate having a first planar surface, and a second substrate layer having a first planar surface, wherein the first planar surface of the second substrate has a lower transition temperature than the first surface of the first substrate. The first surface of the second substrate is heated approximately to the transition temperature. The first surface of the first substrate is bonded to the first surface of the second substrate.
This invention also provides methods of fabricating a microfluidic device comprising a first substrate having at least a first surface and a second substrate having at least a first surface, wherein at least one of the first surface of the first substrate or the first surface of the second substrate comprises a textured surface, and mating and bonding the first surface of the first substrate to the first surface of the second substrate.
This invention also provides methods of fabricating a microfluidic device comprising a first substrate having a first planar surface, and a second substrate layer having a first planar surface, wherein the first planar surface of the second substrate has a lower transition temperature than the first surface of the first substrate. The first surface of the first substrate is thermally bonded to the first surface of the second substrate, whereby the first surface of the second substrate does not substantially project into the plurality of channels.
This invention also provides a microfluidic device comprising a first polymeric substrate having at least a first planar surface, the first planar surface comprising a plurality of channels disposed therein. The device also includes a second polymeric substrate layer having at least a first planar surface, the first planar surface of the second substrate is bonded to the first planar surface of the first substrate, and wherein the first surface of the second substrate has a lower transition temperature than the first surface of the first substrate.
This invention also provides a microfluidic device comprising a first polymeric substrate comprising a first planar surface having a plurality of microscale channels disposed therein. The device also contains a second polymeric substrate comprising a first planar surface, the first planar surface of the second substrate being non-solvent bonded to the first planar surface of the first substrate, wherein the first surface of the second substrate does not substantially project into the plurality of channels.